Generally this would be caused by a broken stem pipe or lateral in your filter. These parts are all usually easy to replace. It is important to know that when you replace the sand in your filter you must backwash your system before turning on the system filter.Â You also must use the right sand – #20 Silica Sand or 45-55 mm pool sand. We always have this in stock at the store. To remove the sand that has made its way into the pool just vacuum with your manual vacuum to waste or drain.